Hafler 9130 feedback loop MOD question - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 4th June 2008, 08:02 PM   #1
reiver is offline reiver  United States
diyAudio Member
 
Join Date: May 2008
Default Hafler 9130 feedback loop MOD question

I have a Hafler 9130 I'm modding with new PP film caps, electrolytics, bypass caps etc.

The feedback loop is very simple compared to other Hafler amps. It uses just a 3pf cap and a 100mf/16v non-polar cap to ground. Other Haflers use a 470mf np cap here, while a popular mod is to use a 1000mf np cap in this spot.

My question is: 100mf seems awfully small. Would using a 470 or 1000mf cap here on this feedback loop cause any issues? Or would it simply open up the low end response?

See the attached image............

-Bryan
Attached Images
File Type: jpg loop.jpg (22.4 KB, 70 views)
  Reply With Quote
Old 4th June 2008, 08:45 PM   #2
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
1/(2xPi x 100^-6F x1100E) seems already pretty low ;

you'll not gain much , going to more than 220uF ;
place nice film cap (1uF) across ....... and enjoy
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
  Reply With Quote
Old 5th June 2008, 01:12 AM   #3
diyAudio Member
 
unclejed613's Avatar
 
Join Date: Dec 2006
it's the DC blocker for the feedback loop. it also sets the LF -3db point of the amp's frequency response, usually at about 5hz. it protects woofers from LF excursions caused by things like warped vinyl records (those big black discs that my kids call "huge CD's"). as long as you aren't using media that can cause such LF signals, it's ok to put a 1000uf in there, but be aware that you'll change the amp's -3db point from 5hz to 0.5 hz, really not neccesary. the other cap (the 3pf) sets the amp's HF -3db point, and usually is used if a design has a tendency towards oscillation. leave this cap as-is.
__________________
Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net
spammer trap: spammers must die
  Reply With Quote
Old 5th June 2008, 02:34 AM   #4
reiver is offline reiver  United States
diyAudio Member
 
Join Date: May 2008
Default re:

Thanks.........good info.

I agree, lowering it from 5hz to .5 isn't worth the soldering time. I noticed that my 9130 was bass-shy compared to my XL280 and was focusing on that cap as the culprit.

I suspect it's the compact 6800mf power supply caps and smaller transformer in the main supply that are more the real cause.

-Bryan
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
WTB Hafler SE-120 or PRO 1200 or 9130 Circuit Board Dick West Swap Meet 5 7th February 2011 10:13 PM
Hafler 9130 Hum db5owat Solid State 25 19th September 2008 03:56 PM
Replacing Hafler 9130 transistors- 2 techie question reiver Solid State 5 12th June 2008 12:15 PM
Hafler 9130/Pro1200 circuit differences? reiver Solid State 1 26th May 2008 04:29 PM
Hafler 9130 amp to sell Dick West Swap Meet 5 2nd December 2005 03:13 AM


New To Site? Need Help?

All times are GMT. The time now is 12:40 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2